Characterization of cores from the Black and Marmara Seas : implications for TOC source and preservation and potential for paleoenvironmental interpretation

Adetona, Kehinde B.
(2005)
Characterization of cores from the Black and Marmara Seas : implications for TOC source and preservation and potential for paleoenvironmental interpretation.
Masters thesis, Memorial University of Newfoundland.

[English]
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[English]
PDF
- Accepted Version
Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
(Original Version)

Abstract

Elemental (carbon, sulphur and biogenic opal) analysis was performed on the bulk sediments recovered from four core sites (MAR00-5, MAR00-6, and MAR00-8) in the Black Sea and core site MAR98-11 in the Marmara Sea. Isotopic (δ¹³C and δ ³⁴S) analysis was also performed on the bulk organic matter in the sediments. Linear extrapolations based on ¹⁴C dates in the three Black Sea cores indicate that while MAR00-6 is characterized by continuous and uniform sediment deposition, cores MAR00-5 and MAR00-8 lack a record of the last ∼5000 years. δ¹³C values from ∼-26‰ to ∼-23‰ for the TOC in the Black Sea cores indicate the mixing of isotopically light land-derived material with isotopically heavier autochthonous carbon derived from primary marine production. Interpretations from proxy data extracted from the cores suggest that relatively higher TOC contents in core MAR00-6 compared to the other Black Sea cores can be explained by better preservation of organic matter. This is attributed to the existence of a more stable stratified water-column well below wave base and/or greater salinity contrast between surface and bottom waters at this site before 5000 yr BP. -- Lithostratigraphic correlation to nearby core MAR98-12 with its ¹⁴C dates places sapropel deposition in core MAR98-11 between ∼9800 to ∼6600 yr BP, which coincides with the contemporaneous sapropel S1 in the Aegean Sea. δ¹³C values, the relatively high terrestrial organic-carbon component and other proxy data during this period point to a predominantly terrestrial source for the organic matter and reduced oxygen levels in the bottom waters. These data from core MAR98-11 broadly support the view of Aksu and coworkers that there has been a sustained brackish outflow from the Black Sea to the Mediterranean Sea via the intervening Marmara Sea since ∼11000-10500 yr BP.